The following U.S. patents are illustrative of the art in the field of the invention.
Wilbur, 932,218, Aug. 24, 1909 for Reel. The line for a plumb bob is wound on a reel spool 18. A brake shoe is normally pressed against the periphery or head 20 of the spool by action of a spring 23. To release the brake shoe, a trigger like button 17 is pressed to compress the spring 23 further and release the brake shoe 18 from engagement with the head 20 permitting the line to be payed out or wound in.
Burns, 1,043,293, Nov. 5, 1912, for Plumb Bob. The bob line is wound upon a reel 7. A brake-ring 15 is actuated by a spring 20 to brake the reel 7. When pay-out is desired, a button 21 is pressed to compress the spring and release the reel.
O'Loughlin, 1,571,667, Feb. 2, 1926, for Plumb Bob Carrier. A plumb carrier winds the cord of the plumb upon a reel mounted on a shaft 24 journaled in bearings. A spiral spring 25 within the reel causes winding of the cord when dogs 27 are in disengagement with cams 26, and when engaged halt the reel, as in window shade operation.
Spaeth et al., 1,876,473, Sept. 6, 1932, for Plumb Bob and Chalk Line. A plumb bob contains a reel on which, by means of an external handle, the line is wound inside the bob to a desired length.
Hoagland, 2,384,917, Sept. 18, 1945, for Plumb Bob Line Reel. The reel container may be fastened to a wall. A set screw 20 may be applied against a flange 2a of the reel 2 in order to hold the line from payout.
Worden, 2,492,609, Dec. 27, 1949, for Brake for Plumb Bob Reels. A plumb bob 15 is reeled upon a reel 13. The handle 20 of the reel may fold inwardly for insertion in the open end of hub 10 of the reel to expand fingers 12 into tight fitting frictional engagement with the hub.
Landon et al., 2,589,500, March 18, 1952, for Combined Chalk Line Box and Plumb Bob. A crank 27 with a handle 48 reels in or pays out the line for a combined plumb bob and case. The crank handle 49 locks in an opening in the case when the device is not in use.
Williams, 2,637,913, May 12, 1953, for Plumb Bob Carrier. A slidable latch 41 engages the reduced neck 44 of a plumb bob in storage so that the bob is secured against or in a container for the line. The latch may be slid to release the neck and free the bob, allowing the line to be paid out.
Unger, 3,011,263, Dec. 5, 1962, for Plumb Bob Device. A reel or spool 3 is mounted rotatably in a case 5 on a shaft 10. An operating crank 11 actuates the spool. Wells or sockets 12 in the case receive the handle 25 of crank 11 for securing the reel or spool against rotation. There is no provision for distributing the line on the reel.
Matson, 3,016,606, Jan. 16, 1962, for Combination Marking Line and Plumb Bob. A marking line 16 has one end fixed to the hub of a reel 3 enclosed in a container having a dye well for marking dye to be applied to the plumb line.
Bosco, 4,459,761, July 17, 1984 for Retractable Plumb and Chalk Line. A crank arm at one end rotates a shaft 20 on which is wound the line of a plumb bob 12. A bell crank member 33 when retracted causes dog-engagement of lugs with the case to prevent unwinding of the line.